Screw for Composite/Plastic Materials

ABSTRACT

A fastener for composite or plastic material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. In one embodiment, the shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/384,269 filed Apr. 2, 2009, which is a continuation-in-part of U.S.patent application Ser. No. 11/973,906 filed Oct. 11, 2007, now U.S.Pat. No. 7,988,396.

BACKGROUND OF THE TECHNOLOGY

This technology relates to fasteners which are employed for fasteningcomposite and plastic materials to a support structure. Moreparticularly, the fasteners relate to deck screws employed for securingdense composite and plastic materials.

Numerous fasteners have been advanced for fastening deck members whichare composed of composite material. Several of these such deck fastenersare directed to eliminating the volcanoing or mushrooming effect. As thetechnology of composite materials has advanced, the denseness of thecomposite members has increased. The increased denseness has had asignificant impact on the effectiveness of conventional deck screws.Accordingly, many deck screws which were adapted to perform in earliercomposite environments are significantly less effective in the moredense material. A significant issue resides in the difficulties ofdriving fasteners into very dense composite materials.

SUMMARY OF THE DISCLOSURE

In one embodiment, a fastener for composite or plastic lumber comprisesa head having a socket rotatably couplable for application of a torqueand having a recessed underside with a lower rim. An elongated shankextends from the head and terminates at a distal tip. The shank has anupper portion with an enlarged diameter and a lower portion with areduced diameter. The upper portion is traversed by a left hand thread.The lower portion has a tri-lobed configuration and is traversed by aright hand thread with the right hand thread having a plurality ofnotches.

The right hand thread may extend substantially to the tip. At least onenotch may be formed in the tip thread. In one embodiment, at least twonotches are formed in the tip thread with at least two notches being outof phase. The notches form a spiral array. A land extends between thethreads. The socket is preferably a square socket. The number of threadsper inch of the left hand thread is less than the number of threads perinch of the right hand thread. The thread angle of the left hand threadis greater than the thread angle of the right hand thread. The left handthread preferably has a minor diameter greater than the minor diameterof the right hand thread.

A screw which is especially adapted for securing trim board materialcomprises an elongated shank which extends from the head and terminatesat a distal tip. A portion of the shank adjacent the head has anenlarged diameter which is traversed by a left hand thread. The lowershank portion has a reduced diameter which does not have a trilobialform but includes a right hand thread with a plurality of notches whichextends substantially to the tip. The number of threads per inch of theleft hand thread is less than the number of threads per inch of theright hand thread. The thread angle of the left hand thread is greaterthan the thread angle of the right hand thread. In one embodiment thescrew has a length of approximately 2.75 inches and the left hand threadextends approximately 0.3 inches.

A screw which is especially adapted for securing extremely densecomposite or plastic material comprises an elongated shank which extendsfrom the head and terminates at a distal tip with an upper portionhaving an enlarged diameter and a lower portion of the shank having areduced diameter. The upper portion is traversed by a plurality of ringshaving a uniform major diameter. The lower portion is traversed by asecond thread with a plurality of notches. In one embodiment, there arethree longitudinally spaced rings which are equidistantly spaced. Therings have an effective minor diameter greater than that of the secondthread.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view, partly in phantom and partly indiagrammatic form, of a deck screw;

FIG. 2 is an end view of a head portion of the deck screw of FIG. 1;

FIG. 2A is an end view of an alternative embodiment of a head portion ofthe deck screw of FIG. 1;

FIG. 3 is an enlarged sectional view, partly in diagrammatic form, of ahead and end portion of the deck screw of FIG. 1 taken along the linesof A-A of FIG. 2;

FIG. 4 is a diagrammatic view illustrating a representative threadprofile for a top portion of the deck screw of FIG. 1;

FIG. 5 is a diagrammatic view illustrating a representative threadprofile for a bottom portion of the deck screw of FIG. 1;

FIG. 6 is a sectional view illustrating the deck screw of FIG. 1 asemployed for securing a composite material to a support structure;

FIG. 7 is an enlarged longitudinal view of a medial portion of the deckscrew of FIG. 1;

FIG. 8 is an enlarged cross-sectional view, partly in diagrammatic form,taken along the lines of B-B of FIG. 7 and rotated 90°;

FIG. 9 is an enlarged fragmentary view, partly in diagrammatic form, ofa tip portion of the deck screw of FIG. 1;

FIG. 9A is an enlarged fragmentary view, partly in diagrammatic form, ofan alternative tip portion of the deck screw of FIG. 1;

FIG. 10 is a sectional view, partly in diagrammatic form, taken alongthe lines of C-C of FIG. 9;

FIG. 11 is a longitudinal side view, partly in diagrammatic form,illustrating a first stage workpiece for the deck screw of FIG. 1;

FIG. 12 is a longitudinal sectional view, partly in diagrammatic form,of a second stage workpiece for the deck screw of FIG. 1;

FIG. 13 is an end view of the workpiece of FIG. 12;

FIG. 14 is a longitudinal view, partly in diagrammatic form, and partlyin phantom, of a third stage workpiece for the deck screw of FIG. 1;

FIG. 15 is an enlarged sectional view, partly in phantom and partly indiagrammatic form, taken along the lines D-D of FIG. 14;

FIG. 16 is a longitudinal view, partly in phantom and partly indiagrammatic form, of another embodiment of a screw suitable forsecuring trim board; and

FIG. 17 is a longitudinal view, partly in phantom and partly indiagrammatic form, of yet another embodiment of a deck screw.

DETAILED DESCRIPTION

With reference to the drawings wherein like numerals represent likeparts throughout the several views, a deck screw is generally designatedby the numeral 10. Deck screw 10 is especially adapted for securingelongated deck members 20 to a support member 22 wherein the compositematerial is a highly dense material such as, for example, Trex™ deckmaterial, Timber Tech™ deck planks, etc. As illustrated in FIG. 6, thedeck screw 10 functions to be driven through the composite member 20into the support structure 22 to a depth wherein the head is below theupper surface of the material and forms a cylindrical counterbore abovethe head. The deck screw 10 can be driven without volcanoing ormushrooming of the material around the head and can be relatively easilydriven without intense resistance to the application of torque duringthe driving process.

With reference to FIG. 1 the deck screw 10 includes a head 30 and anelongated shank 40 which extends from the head and has a generallybifurcated form. In one embodiment, the screw length l1 is 2.75 ins witha head diameter dl of 0.285 ins. The shank 40 has an upper portion 42 oflength l2 of enlarged nominal diameter and a lower portion 44 of lengthl3 of reduced nominal diameter which has a distal tip 46. The tipterminates in a well-defined vertex point 48 which in the preferred formhas a vertex angle of 25 degrees. The tip 46 functions as a drill point.

With additional reference to FIGS. 2 and 3, the head 30 includes arecess 32 which at an upper portion is defined by a #1 square socket 34and is adapted for coupling with a torque driver bit (not illustrated).Socket 34 preferably has a minimum depth of 0.075 ins and preferably adepth from .075 ins to .095 ins. If the socket depth is too shallow, thehead will disengage during driving. If the head is too deep, thestructural integrity of the head is jeopardized. The corners of thesocket 34 may be rounded (not illustrated).

With reference to FIG. 2A, an alternative socket 34A is defined by 8radial slots and is adapted for coupling with a torque driver (notillustrated). The coupling socket 34A may be similar in form andfunction to that described co-pending U.S. patent application Ser. No.11/185,377 filed Jul. 20, 2005 which is assigned to the applicant of thepresent invention and the disclosure of which is incorporated byreference. The eight point torque driving engagement provides anefficient coupling engagement to facilitate torqueing of the deck screwand mitigate against disengagement of the tool during the drivingprocess.

The head 30 includes a tapered skirt-like periphery 36 which includes arecessed underside 38 and a lower cutting rim 39. In one form, the angleof the underside flaring is on the order of 39 degrees as illustrated inFIG. 3. The head socket 34 is adapted to efficiently couple with thedriver. The underside 38 of the head is configured to prevent compositematerial from being displaced past the head during the driving processand for capturing the composite material and trapping same at itsunderside. The cutting rim 39 is adapted to provide a clean, circularopening in the composite material and to present a pleased, finishedsetting of the deck screw in the drive bore so that the top surface ofthe head is below the surface of the dense composite material (FIG. 6).

The shank 40 has an upper portion 42 proximate the head which has alarger diameter than that of the lower portion 44. In one embodiment,the upper portion 42 includes a left hand thread 52 which extends alength l7 or approximately 0.750 inches and is 9 threads per inch.Thread 52 has a thread angle of 48 degrees as illustrated in FIG. 4. Ina preferred embodiment of thread 52, the minor thread diameter is 0.133inches and the major thread diameter is 0.210 inches.

Various approximate dimensions for one embodiment are summarized inTable I.

TABLE I d1 0.285 ins  l1 2.75 ins l2 0.80 ins l3 1.75 ins l4 0.02 ins l50.10 ins l6 0.12 ins l7 0.75 ins

In another embodiment l7 is approximately 0.45 ins. and l3 isapproximately 1.675 ins.

As will be further described, the lower shank portion 44 also has atri-lobe configuration as best illustrated in FIG. 15. The lower shankportion 44 is traversed by a right hand thread 54 which is 12 threadsper inch and has an included thread angle of 30 degrees as illustratedby the profile of FIG. 5. A preferred embodiment of thread 54 has aminor diameter and of 0.123 inches and a major diameter Md of 0.190 to0.196 inches.

With reference to FIGS. 1 and 7, the thread 54 for a length l8 ofapproximately 0.5 to 0.9 inches is traversed by a spiral array ofnotches 60. As best illustrated in FIG. 8, the spiral array 60 subtendsan angle of approximately 90 degrees about the shank axis with the depthof each notch being approximately the minor diameter. The notch widthnw1 is approximately 0.10 inches. The spiral array 60 extendsapproximately 1 revolution per 1.5 inches in length.

With reference to FIG. 9, the shank terminates in the tip 46 whichcontinues the spiral thread 54. A notch 62 is shown in section. Thewidth nw2 may be longer for notch 62. In some embodiments, only onenotch may be employed for the tip. If two notches are employed, thesecond notch 64 is slightly out of phase to create a split point. Thenotches 62, 64 may extend to a depth slightly into the minor diameter atthe tip as illustrated in FIG. 10. The depth wd2 of the notch is 0.12inches. Another tip 46A having a blunt point with notches 62A and 64A isillustrated in FIG. 9A.

Representative dimensions for lower portion 44 for a preferredembodiment are set forth in Table II.

TABLE II l8 0.5 to 0.9 ins nw1 0.10 ins nd2 0.12 ins md 0.123 ins Md0.190 to 0.196 ins

The manufacturing process for the deck screw 10 is best illustrated inthe FIGS. 11-15. The initial work piece cut off shown as 10A in FIG. 11has a workpiece diameter wd1 of 0.15 ins and a workpiece length wl1 of2.70 ins. The first blow shown in FIG. 12 produces workpiece 10B whichforms the bifurcated shank portions 425, 44B and the head 30B withworkpiece lengths wl2 of 2.68 ins and wl3 of 0.125 ins and workpiecehead diameter wd2 of 0.250 ins. The coupling recess 32 is then punchedinto the head portion to form the final head detail as shown in FIG. 3.

FIG. 14 shows the tri-lobe formed shank portion 44A for the workpiece10C. The dimensions for workpieces 10A, 10B and 10C are given in TableIII for a screw 10 having a final length l1 of 2.75 ins.

TABLE III l1  2.75 ins Wd3 0.137 ins wl1  2.70 ins wd1  0.15 ins wl2 2.68 ins wd2 0.250 ins wl3 0.125 ins wl4  2.69 ins wl5 1.715 ins wl60.875 ins wl7 0.115 ins

The threads 52, 54 are then rolled onto the workpiece 10C. The notches60 and 62 are then punched into the workpiece. Alternately, the notchesmay be formed during the thread forming process.

With reference to FIG. 16, a screw which is especially adapted forsecuring trim board for composite or plastic materials is designated bythe numeral 110. The trim board typically has a plastic composition.Screw 110 does not have a trilobial form as previously described withrespect to deck screw 10. The screw 110 is efficiently configured to bedriven through trim board of composite material into a composite memberor a support structure. The screw 110 is preferably driven a depth inthe trim board (not illustrated) wherein the head 130 is sunk below theupper surface of the material (not illustrated) and forms a cylindricalcounter bore above the head. The screw can be driven without volcanoingor mushrooming of the material around the head and can be relativelyeasily driven without intense resistance to the application of torqueduring the driving process.

The head 130 is substantially identical in form and function to head 30.A representative embodiment of screw 110 is hereinafter described. Thelength of I₁ of one embodiment of the screw 110 is 2.750 ins. with thehead diameter of 0.26 ins. The shank 140 has an enlarged diameter neck141 and an extended portion 142. A lower portion 144 of length I₃ of1.900 ins. with a distal tip 146 is substantially similar in form andfunction to tip 46. Portion 142 has a larger diameter than portion 144.

The portion 142 includes a left hand thread 152 which extends a lengthI₂ of approximately 0.300 ins. The thread 152 has 9 threads per inchwith a 48 degree included angle, such as illustrated by the FIG. 4profile. The thread 152 in one embodiment has a minor diameter of 0.133ins. and a major thread diameter 0.250 ins.

The lower shank portion 144 is traversed by a right hand thread of 12threads per inch and has an included thread angle of 30 degrees, asillustrated by the FIG. 5 profile. A preferred embodiment of thread 154has a minor diameter of 0.123 ins. and a major diameter of 0.185 to0.191 ins. The remaining portions are substantially similar to thatdescribed for deck screw 10 and include a spiral array of notches 160with notches in the tip being substantially the same as described withrespect to deck screw 10.

Various approximate dimensions for one embodiment of trim screw 110 aresummarized in Table IV.

TABLE IV l₁ 2.750 ins l₂ 0.300 ins l₃ 1.900 ins l₄ 0.060 ins l₅ 0.105ins l₆ 0.850 ins l₇ 0.375 ins

With reference to FIG. 17, deck screw 210 is especially adaptable foruse with very dense material, such as, for example, Trex Escapes™ andEverGrain™ composite or plastic materials. A representative embodimentof deck screw 210 is hereinafter described. Deck screw 210, in oneembodiment, has a length L₁ of 2.75 ins. and a head diameter of 0.26ins. The upper portion 242 of the shaft includes an enlarged neck 241which extends for a length of 0.20 inches and an adjacent shank portion242 which extends a length L₂ for 0.900 ins.

Three rings 251, 252, 253 are formed on an intermediate shank portion243. In one embodiment, the rings have an included angle of 30 degreeswith an effective minor diameter of 0.133 ins. (the nominal diameter ofportion 242) and a major diameter between 0.205 and 0.210 ins. The rings251, 252, 253 are substantially identical and are spaced apart a pitchdistance of approximately 0.121 ins.

The rings 252, 252, 253 have an included thread angle of 30°, such asillustrated in FIG. 5. The lower shank portion 244 is substantiallyidentical to that of lower shank portion 154.

Various approximate dimensions for one embodiment of deck screw 210 aresummarized in Table V.

TABLE V L₁  2.75 ins L₂ 0.900 ins L₃ 1.675 ins L₄ 0.200 ins L₅ 0.105 insL₆ 0.900 ins L₇ 0.700 ins L₈ 0.121 ins

While preferred embodiments have been set forth for purposes ofillustration, the foregoing description should be deemed a limitation ofthe invention herein. Accordingly, various modifications, adaptationsand alternatives may occur to one skilled in the art without departingfrom the spirit and the scope of the present invention.

What is claimed:
 1. A fastener for composite or plastic materialcomprising: a head having a socket rotatably couplable for applicationof a torque and having a recessed underside and a lower rim; anelongated shank extending from said head and terminating at a distal tipand comprising an upper portion having an enlarged diameter and a lowerportion having a reduced diameter; said upper portion being traversed bya left-hand thread; and said lower portion traversed by a right-handthread, said right-hand thread having a plurality of notches.
 2. Thefastener of claim 1 wherein said right-hand thread extends substantiallyto said tip.
 3. The fastener of claim 2 comprising at least one notch insaid tip thread.
 4. The fastener of claim 3 wherein there are at leasttwo notches in said tip thread, two of said notches being out of phase.5. The fastener of claim 1 wherein said notches form a spiral array. 6.The fastener of claim 1 wherein a land extends between said threads. 7.The fastener of claim 1 wherein the fastener has a length ofapproximately 2.750 ins. and the left hand thread extends approximately0.300 ins.
 8. The fastener of claim 1 wherein the number of threads perinch of the left-hand thread is less than the number of threads per inchof the right-hand thread.
 9. The fastener of claim 1 wherein the threadangle of the left-hand thread is greater than the thread angle of theright-hand thread.